Fat soluble vitamins Flashcards
Vitamin A family
retinoids
Most abundant carotenoid eaten by people
beta carotene -carrots
Where is retinol stored
Liver and adipose tissue
What is retinol stored as
retinyl esters
Vitamin A is essential for
vision
Retinyl esters are hydrolyzed in the intestinal lumen into what
FFA and retinol
How much vitamin A does the liver store
6-12 month supply
Liver supplies target tissues with Vitamin A in what form
Retinol bound to retinol binding proteins
RBP-retinol complex associates with what in the blood
transthyretin
Functions of vitamin A
Gene regulation, antioxidant, vision
Form of vitamin A that functions in gene regulation
All-trans retinoic acid
Major target tissues for gene regulation
epithelial cells
Epithelial cells dont synthesize ____ if they’re supplied with enough retinal to make retinoic acid
Keratin
What cells dont normally keratinize
Internal epithelial cells
What cells do normally keratinize
epidermal epithelial cells because they aren’t vascularized
In what environment does vitamin A function as an anti-oxidant
lipid rich environments
Primary anti-oxidant form of Vitamin A
caroternoids
Severe hypovitaminosis
xeroplanthia (progressive keratinization of the cornea leading to blindness)
Mild hypovitaminosis
night blindness, follicular hyperkeratosis
Special needs for vitamin A
Premature infants, fat malabsorption syndromes
Sources of vitamin A
Liver, dark green/ yellow vegetables
What activates the cholesterol metabolite in our skin to form vitamin D3
UV light (290-315 nm)
Cholecalciferol has to undergo what to become the active form of vitamin D
2 hydroxylations
Where does the first hydroxylation occur & catalyzed by what
Liver - CYP2R1
Where does the 2nd hydroxylation occur, what enzyme
Kidney, CYP27B1
What is the active form of vitamin D
1,25-diOH- cholecalciferol
Function of 1,25-diOH- cholecalciferol
Acts alone as a steroid
What does 1,25-diOH- cholecalciferol induce the synthesis of
A protein required for calcium absorption
What does 1,25-diOH- cholecalciferol act synergistically with
PTH to promote bone resorption - or to inhibit calcium excretion in the kidney by stimulating calcium reabsorption
Principal role of vitamin D
CALCIUM HOMEOSTASIS
Vitamin D deficiency in kids
Rickets
Vitamin D deficiency in adults
osteomalacia
Dietary sources
Saltwater fish, liver, egg yolk
Vitamin E- only form that meets human needs
Alpha- tocopherol
Main function of vitamin E
Antioxidant -cell membrane integrity
Vitamin E hypovitaminosis
Increased fragility of RBC membranes
Best sources of vitamin E
vegetable oils
Vitamin K main function
Gamma- carboxylation of glutamate residues
K is important for synthesis of
pre coagulation factors
Sources of K
Intestinal flora produce half RDA
Vitamin K hypovitaminosis
Hemorrhage- predisposed if parenteral nutrition, liver dysfunction, or malabsorption syndrome
Vitamin K is given to who
newborns
Special needs of K
Counteract overdoses of Coumadin anticoagulants, counteract antibiotic therapy
